A cone beam CT (CBCT: Cone Beam Computed Tomography) apparatus is known which reconfigures three-dimensional CT data of an object on the basis of a plurality of transmission images picked up by using a conically-shaped (cone-shaped) X-ray irradiated from a radiation source which rotates around the object. Such a cone beam CT apparatus can generate the three-dimensional CT data in a short time without rotating the radiation source plural times. In a case of employing a patient being as an picked up object, the patient as the picked up object has to stop breathing during the pick-up, in order to obtain a high-precision image free from the blurring of the picked up object caused by a respiratory movement. It is desired to shorten the pick-up time of the transmission image to reduce a strain of the patient.
When a rotation speed of the radiation source is increased, the pick-up time of the cone beam CT apparatus can be shortened. In order to rotate the radiation source safely at a high speed, a device such as a rotating portion of a large-size detector needs to be safely accommodated in a protection cover, and thereby the apparatus will become large and complicated and accordingly will be expensive. It is desired to carry out the high-speed CBCT pick-up without increasing the rotation speed.
Japanese Patent No. 3,940,747 discloses an X-ray diagnostic apparatus which can reduce a rotation angle so as to be less than 180°. The X-ray diagnostic apparatus reconfigures the three-dimensional data of a specimen on the basis of a plurality of X-ray projection images picked up at different angles around the specimen. In the X-ray diagnostic apparatus, when a relation of β>α (α represents a spread angle of the X-ray beam) is satisfied, at least two pairs of imaging systems of an X-ray tube and an X-ray detector are provided to intersect at 90° with each other. A plurality of X-ray projection images are picked up at different angles in a range from 0° to (90+β)° by one of the imaging systems, and a plurality of X-ray projection images are picked up at different angles in a range from 90° to (180+β)° by the other one of the imaging systems. A sensitivity difference between the two imaging systems is calculated from two of the X-ray projection images picked up at the same angles in a range from 90° to (90+β)° by two pairs of the imaging systems before injection of a contrast medium, the sensitivities of a plurality of X-ray projection images picked up by the pairs of the imaging systems after the injection of the contrast medium is corrected on the basis of the sensitivity difference. The three-dimensional data of the specimen is reconfigured from the plurality of X-ray projection images whose sensitivities have been corrected.